Thermal management of electronic devices

ABSTRACT

Thermal management is provided for a device. The device may include a substrate having a mounting area on a first surface of the substrate. The device may also include first thermal vias extending from the mounting area to at least an interior of the substrate. The device may also include at least one thermal plane substantially parallel to the first surface of the substrate, the at least one thermal plane being in thermal contact with at least one of the first thermal vias. The device may also include a heat sink attachment area, and second thermal vias extending from the heat sink attachment area to the interior of the substrate, the at least one thermal plane being in thermal contact with the second thermal vias.

RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.11/363,095, filed Feb. 28, 2006, which is incorporated herein byreference.

FIELD OF THE INVENTION

Implementations consistent with the principles of the invention relategenerally to heat dissipation and, more particularly, to systems andmethods of heat transfer through a substrate supporting electroniccomponents to control operating temperatures of the electroniccomponents.

BACKGROUND OF THE INVENTION

Physical compactness of electronic devices, such as interface devicesmounted at a user interface edge of an electronic assembly, impedescooling of the electronic devices, which is a particular concern forelectronic devices that consume a substantial amount of power, and thusgenerate a significant amount of heat. For example, when transceivers,such as small form-factor pluggable (SFP) modules, are ganged intomultiple cages, the transceivers in the middle of the cluster maygenerate and retain an undesirable amount of heat. Very little airflowmay reach individual modules in certain positions of the cluster forcooling purposes. Unlike stand-alone devices, which have relativelylarge surface areas that may radiate heat, clustered devices may haveonly limited surface area from which to radiate heat.

SUMMARY OF THE INVENTION

According to one aspect, a device may include a substrate that mayinclude a first mounting area on a first surface of the substrate. Thedevice may also include a group of first thermal vias extending from thefirst mounting area to at least an interior of the substrate. The devicemay also include at least one thermal plane substantially parallel tothe first surface of the substrate, the at least one thermal plane beingin thermal contact with at least one of the first thermal vias. Thedevice may also include a heat sink attachment area. In addition, thedevice may include a group of second thermal vias extending from theheat sink attachment area to the interior of the substrate, the at leastone thermal plane being in thermal contact with the second thermal vias.

According to another aspect, a method of heat transfer in a substratemay include conducting heat from a component to a component mountmounted on a first mounting surface of the substrate. The method mayalso include conducting the heat from the component mount to a first setof thermal vias that extend from the first mounting surface to at leastan interior of the substrate. The method may also include conducting theheat from the first set of thermal vias to one or more thermal planesdisposed along a length of the substrate. The method may also includeconducting the heat from the one or more thermal planes to a second setof thermal vias. The method may also include conducting the heat fromthe second set of thermal vias to a heat sink attachment surface of thesubstrate. In addition, the method may include conducting the heat fromthe heat sink attachment surface of the substrate to a heat sink mountedto a heat sink attachment surface of the substrate.

According to yet another aspect, a method of forming a substrate mayinclude disposing one or more thermal planes in the substrate. Themethod may also include providing a first set of thermal vias in acomponent mounting area on a first side of the substrate, the first setof the thermal vias being thermally coupled to the component mountingarea and to the one or more thermal planes. In addition, the method mayinclude providing a second set of thermal vias extending from a heatsink attachment area on the first side of the substrate, the second setof the thermal vias being thermally coupled to the one or more planesand to the heat sink attachment area.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate an implementation of theinvention and, together with the description, explain the invention. Inthe drawings,

FIG. 1 is a diagram illustrating an exemplary device in which methodsand systems consistent with the principles of the invention can beimplemented;

FIG. 2 is an exemplary diagram of the interface card of FIG. 1 accordingto an implementation consistent with the principles of the invention;

FIG. 3 is a cut-away view of an exemplary interface card in whichmethods and systems consistent with the principles of the invention canbe implemented;

FIGS. 4A, 4B, and 4C illustrate an exemplary interface unit in whichmethods and systems consistent with the principles of the invention canbe implemented;

FIG. 5 is a line image of the exemplary daughterboard of FIGS. 4A-4C;and

FIG. 6 is a flow diagram of an exemplary thermal management processaccording to an implementation consistent with the principles of theinvention.

DETAILED DESCRIPTION

The following detailed description of embodiments of the principles ofthe invention refers to the accompanying drawings. The same referencenumbers in different drawings may identify the same or similar elements.Also, the following detailed description does not limit the invention.Instead, the scope of the invention is defined by the appended claimsand equivalents.

Systems and methods consistent with the principles of the invention mayprovide controlled cooling of a component, such as an input/outputdevice, that may be located in a compact configuration at a userinterface edge of an interface card, by conducting heat away from thecomponent using a system of thermally coupled thermal vias and thermalplanes on and/or in a substrate to a heat sink that may be disposed inan available airflow that may flow by the interface card.

Exemplary Device Configuration

FIG. 1 illustrates an exemplary device 100 in which systems and methodsconsistent with the principles of the invention may be implemented. Asillustrated, device 100 may include a housing 110 that houses variousmodules 120 (e.g., controller, power supply, etc.) and card slots 130which operably receive interface cards 140.

In one implementation, device 100 may include any device that receives,processes, and/or transmits data, such as a server, a router, or aswitch.

In one implementation, housing 110 may include any structureconfigurable to retain and/or support a chassis, removable cards, and/orother modules that may be used in operation of device 100. The numberand type of cards, modules, and other system components illustrated inFIG. 1 are provided for simplicity. In practice, a typical device couldinclude more or fewer cards, modules, and other removable or fixedcomponents that aid in receiving, processing, and/or transmitting data,than what is illustrated in FIG. 1. Housing 110 may be fabricated frommetal, plastic, and/or composite and may be sized for particularapplications. In one implementation, housing 110 may be sized to fit anindustry standard mounting structure, such as an equipment rack.

FIG. 2 illustrates exemplary interface card 140 in an orientationrepresentative of being configured in card slot 130 in housing 110 (FIG.1), for which airflow may be represented by the directional arrowsshown. It should be appreciated that the cooling effect produced by theairflow may not be uniform over the various surfaces of interface card140.

FIG. 3 illustrates an internal view of one end of an exemplary interfacecard 340. Interface card 340 may include a motherboard 350 and aninterface unit 360. Motherboard 350 may include any substrate, such as acircuit board, e.g., a printed circuit board (PCB). Interface card 340may include more than one interface unit 360.

Interface unit 360 may include a daughterboard 362, interface modulecages 364 for receiving interface modules 366, and heat sinks 368. Inone implementation, interface modules 366 may attach directly todaughterboard 362 and interface module cages 364 are omitted. Interfaceunit 360 may include any input/output device, such as a smallform-factor pluggable (SFP) interface, an XFP (10 Gigabit SFP), or anytype of transceiver. Interface unit 360 may electrically, structurally,and/or thermally connect to motherboard 350. Interface unit 360 may belocated at a user-accessible end of motherboard 350. Otherconfigurations are possible.

Daughterboard 362 may include any substrate, such as a PCB.Daughterboard 362 may have any dimensions corresponding to thedimensions of interface card 340. In one implementation, motherboard 350may include interface unit 360. That is, motherboard 350 and interfaceunit 360 may be an integral PCB, without a separate daughterboard 362.

Interface module cages 364 may include any device for receiving andretaining interface modules 366. Interface module cages 364 may includeganged individual module cages. Other configurations of interface modulecages 364 are possible. As shown, interface module cages 364 may bearranged on opposing sides of daughterboard 362. Interface modules 366may include any electronic component and/or circuitry, such as an SFPmodule, e.g., an SFP optical modular transceiver. In one implementation,interface modules 366 are hot-swappable.

Heat sinks 368 may include any device that may absorb, conduct, radiate,and/or dissipate heat. Heat sinks 368 may include any material havingany thermal conductivity. Heat sinks 368 may have any shape ordimensions. Any number of heat sinks 368 may be used. Thermalconductivity properties of any one heat sink 368 may vary from anotherheat sink 368. As shown, heat sinks 368 may be disposed at a remote endof daughterboard 362. Other configurations of the heat sinks 368 arepossible. For example, heat sinks 368 may be disposed on two or moresurfaces on daughterboard 362. In one implementation, the location ofheat sinks 368 is based on an airflow in device 100.

FIGS. 4A and 4B illustrate opposing views of an exemplary interface unit360. As shown, interface unit 360 may include four interface modulecages 364, two side-by-side mounted at a mounting area of a firstsurface of daughterboard 362, and two side-by-side mounted at a mountingarea of an opposite second surface of daughterboard 362 along anaccessible edge of interface unit 360. Other configurations may be used.Any mechanism may be used to mount interface module cages 364 todaughterboard 362. In one implementation, a thermal interface material(not shown) is interposed between a mounting surface of interface modulecages 364 and the mounting area on the surface of daughterboard 362. Asshown, two interface modules 366 are respectively plugged into twointerface module cages 364. Interface unit 360 may include heat sinks368 attached to daughterboard 362 at an attachment area by attachmentmembers 470 (FIG. 4B). Other attachment mechanisms may be used. In oneimplementation, a thermal interface material (not shown) is interposedbetween a mounting surface of heat sinks 368 and the attachment area onthe surface of daughterboard 362.

FIG. 4C illustrates an exploded view of interface unit 360.Daughterboard 362 may include thermal vias 480A that terminate on asurface of daughterboard 362 in an area of interface module cages 364and terminate on an opposing surface of daughterboard 362. Daughterboard362 may include thermal vias 480B that terminate on a surface ofdaughterboard 362 in an area of heat sinks 368 and extend to an interiorof daughterboard 362. Daughterboard 362 may include thermal planes 490.Thermal planes 490 may be exposed at the edge of daughterboard 362.Thermal planes 490 may alternatively not be exposed at the edge ofdaughterboard 362. Thermal planes 490 may be electrically insulated fromelectrical connections, electrical vias, or electrical planes. Thermalplanes may alternately include power planes, ground planes, and thelike.

FIG. 5 illustrates a partial line image of daughterboard 362, showing aninternal construction thereof. Thermal vias 480A and 480B may includeone or more through-holes that extend from a surface of daughterboard362 to an interior of daughterboard 362. In one implementation, thermalvias 480A and 480B may extend from one surface of daughterboard 362 toan opposing surface of daughterboard 362. Thermal planes 490 may includeone or more thermal conducting layers separated by substrate layers ofdaughterboard 362. Thermal planes 490 may be configured substantiallyparallel to daughterboard 362. Thermal planes 490 may extend fromthermal vias 480A to thermal vias 480B. Thermal planes 490 may beexposed at an edge of daughterboard 362. Any of thermal vias 480A maythermally couple to any or each of thermal planes 490, and any ofthermal planes 490 may thermally couple to any or each of thermal vias480B.

Thermal vias 480A and 480B may form a uniform pattern on the surface ofdaughterboard 362. Thermal vias 480A and 480B may alternatively benon-uniformly arranged on the surface of daughterboard 362. Thermal vias480A and 480B may extend substantially perpendicularly from the surfaceto an interior of daughterboard 362. Thermal vias 480A and 480B mayalternatively extend at any angle from the surface to an interior ofdaughterboard 362. Thermal vias 480A and 480B may have a substantiallycircular cross-section. Thermal vias 480A and 480B may alternativelyhave cross-sections of any other regular or irregular shape. Thermalvias 480A and 480B may have any diameter that is substantially constantfrom end to end. Thermal vias 480A and 480B may alternatively havediameters that vary over a length thereof. Any of thermal vias 480A and480B may vary one from another in any of the above respects.

A periphery of thermal vias 480A may correspond to a perimeter ofinterface module cages 364, i.e., define a mounting area for interfacemodule cages 364 on a surface of daughterboard 362. The total effectivesurface area of thermal vias 480A at the surface of daughterboard 362may constitute any portion of the total area of the mounting area ofinterface module cages 364. Some of thermal vias 480A may alternativelynot be covered by interface module cages 364. Alternatively, themounting surfaces of interface module cages 364 may overlap theperiphery of thermal vias 480A.

A periphery of thermal vias 480B may correspond to a perimeter of heatsinks 368, i.e., define a mounting area for heat sinks 368 on a surfaceof daughterboard 362. The total effective surface area of thermal vias480B at the surface of daughterboard 362 may constitute any portion ofthe total area of the mounting area of heat sinks 368. Some of thermalvias 480B may alternatively not be covered by heat sinks 368.Alternatively, the mounting surfaces of heat sinks 368 may overlap theperiphery of thermal vias 480A.

Thermal vias 480A and 480B may include blind vias that extend from asurface of daughterboard 362 to a predetermined depth of daughterboard362. Thermal vias 480A and 480B may include backdrilled vias that extendfrom a predetermined depth of an interior of daughterboard 362 toanother predetermined depth of an interior of daughterboard 362. In oneimplementation, backdrilled vias may interconnect one or more thermallayers 490.

Thermal vias 480A and 480B may include plated through-holes. The platingmay be disposed on all or any portion of the circumference of thethrough-holes. The plating may be any one or more materials having anythermal conductivity. The plating may occupy any portion of the volumeof the through-holes. The plating may form a hollow cylinder having anouter diameter and an inner diameter. In one implementation, the innerdiameter of the plating may be filled or partially filled with a secondmaterial, for example, a soldering material. Any of thermal vias 480Aand 480B may vary one from another in any of the above respects.

Thermal planes 490 may include any of one or more materials having anythermal conductivity. In one implementation, thermal planes 490 mayinclude a thermal conductive layer on all or any portion of a surface ofdaughterboard 362. Thermal planes 490 may have a substantially constantcross-section. Thermal planes 490 may alternatively have a varyingcross-section along a length thereof. Any of thermal planes 490 may varyone from another in any of these respects. In one implementation, forexample, an inner-most thermal plane 490 may have the largest effectivecross-sectional area relative to other thermal planes 490. In anotherimplementation, a thermal plane 490 that is the greatest distance frominterface module cages 364 may have the largest effectivecross-sectional area relative to other thermal planes 490.

Daughterboard 362 may be formed according to any standard technique forforming a PCB. For example, a layer of copper may be affixed to a layerof an insulating substrate. Patterns may be etched in the copper layer.Additional copper/insulating layers may be laminated to the substratewith etched patterns. In one implementation, a four-ounce copper is usedfor the copper layers. Other thicknesses of copper may be used. Thethickness of the copper may be thicker by any factor than a copper layerthickness (e.g., ½ oz.) used for electrical connections. Through-holesmay be drilled, backdrilled, or otherwise formed in the copper/insulatorlayers. The through-holes may be plated by electrolytic plating or anyother suitable technique. In one implementation, a soldering material isthen flowed in the plated through-holes.

The dimensions and geometries of thermal vias 480A and 480B and/orthermal planes 490 may be based on factors such as structural integrity,electrical connectivity, and optimal thermal conductivity. For example,thermal vias 480A and 480B and thermal planes 490 may be electricallyinsulated from electrical connections (not shown) in daughterboard 362.As another example, thermal vias 480A and 480B and/or thermal planes 490may be formed based on heat generation and/or thermal sensitivity ofparticular interface modules 366, as described in more detail below.

Exemplary Thermal Management

FIG. 6 is a flowchart of exemplary thermal management 600 in a device,such as device 100, according to an implementation consistent withprinciples of the invention. Thermal management 600 may begin withgeneration of heat from interface module 366, such as an activetransceiver, during operations performed by device 100 (act 610). Atleast a portion of the generated heat may be conducted to an interfacemodule cage 364, in which interface module 366 is plugged (act 620). Atleast a portion of the heat absorbed by interface module cage 364 may beconducted to thermal vias 480A having a terminal end in an area directlyunder or near a mounting surface of interface module cage 364 (act 630).In one implementation, one or more thermal vias 480A may directlycontact interface module cage 364. At least a portion of the heatconducted to the one or more thermal vias 480A may be conducted to oneor more thermal planes 490 (act 640). At least a portion of the heatconducted by the one or more thermal planes 490 may be conducted tothermal vias 480B (act 650). At least a portion of the heat conducted tothermal vias 480B may be conducted to heat sink 368, an attachmentportion thereof which may be directly over or near a terminal end ofthermal vias 480B (act 660). At least a portion of the heat absorbed byheat sink 368 may be dissipated into available airflow in device 100(act 670).

It will be appreciated that thermal management 600 may instead beinitiated by interface module 366, such as an inactive transceiver,which acts as a secondary heat source, having absorbed heat from aprimary source that has generated the heat (e.g., an active transceiveror other component).

In one implementation, the heat path described above may be specific toan associated individual interface module cage 364 in interface unit360. That is, the effective heat conductivity of an associated heat pathmay be managed for any given interface module cage 364. The effectiveheat conductivity of an associated heat path may be based on suchfactors as the location of the individual interface module cage 364 ininterface unit 360, the performance level (i.e., heat generation) ofinterface module 366 associated with the individual interface modulecage 364, the heat sensitivity of interface module 366 associated withthe individual interface module cage 364, and thermal gradientsexperienced over interface unit 360, generally. In this manner, the heattransfer rate (i.e., cooling effect) may be managed from one interfacemodule 366 to another.

Optimizing thermal transfer among interface modules 366, or varying theeffective thermal conductivity associated with particular heat paths,may be achieved through the geometries of and interconnection formed bythermal vias 480A and 480B and thermal planes 490. For example, thermalvias 480A may have effective thermal conductivities that differ one fromanother; thermal planes 490 may have effective thermal conductivitiesthat differ one from another; and/or thermal vias 480B may haveeffective thermal conductivities that differ one from another. Sets ofthermal vias 480A associated with particular areas of daughterboard 362may differ one from another.

Conclusion

Implementations consistent with the principles of the invention makepossible efficient heat management in a device employing PCBs havingclustered components, including an interface device, a memory, aprocessor, and other types of devices. For example, heat transfer may beoptimized for any given input/output module through interconnected viasand thermal planes in a substrate of an interface unit of an interfacecard, thereby controlling the temperature of the input/output module.

The foregoing description of exemplary embodiments of the inventionprovides illustration and description, but is not intended to beexhaustive or to limit the invention to the precise form disclosed.Modifications and variations are possible in light of the aboveteachings or may be acquired from practice of the invention.

For example, implementations consistent with the principles of theinvention can be implemented using assemblies and parts other than thoseillustrated in the figures and described in the specification withoutdeparting from the spirit of the invention. Parts may be added and/orremoved from device 100, interface unit 360, and/or daughterboard 362depending on specific deployments and/or applications. Further,disclosed implementations may not be limited to any specific combinationof components.

No element, act, or instruction used in the description of the inventionshould be construed as critical or essential to the invention unlessexplicitly described as such. Also, as used herein, the article “a” isintended to include one or more items. Where only one item is intended,the term “one” or similar language is used. Further, the phrase “basedon,” as used herein is intended to mean “based, at least in part, on”unless explicitly stated otherwise.

The scope of the invention is defined by the claims and theirequivalents.

1. A method of heat transfer in a substrate, comprising: conducting heatfrom a component to a component mount mounted on a first mountingsurface of the substrate; conducting the heat from the component mountto a first set of thermal vias that extend from the first mountingsurface to at least an interior of the substrate; conducting the heatfrom the first set of thermal vias to one or more thermal planesdisposed along a length of the substrate, where a particular one of theone or more thermal planes is exposed at one surface edge of thesubstrate and is not exposed at an opposing surface edge of thesubstrate; conducting the heat from the one or more thermal planes to asecond set of thermal vias; and conducting the heat from the second setof thermal vias to a heat sink mounted to a heat sink attachment surfaceof the substrate, wherein the attachment surface is the first mountingsurface perpendicular to the exposed surface edge of the substrate. 2.The method of claim 1, further comprising: conducting the heat from thesecond set of thermal vias to a heat transfer material interposedbetween the second set of thermal vias and a mount portion of the heatsink.
 3. The method of claim 1, where the conducting the heat from thefirst set of thermal vias to the one or more thermal planes comprisesconducting the heat via through-holes including a first material havinga first thermal conductivity and a second material having a secondthermal conductivity.
 4. The method of claim 1, where the first set ofthe thermal vias comprise a non-uniform distribution at the firstmounting surface.
 5. The method of claim 1, where the conducting theheat from the component mount to the heat sink comprises a first thermalpath, a first thermal conductivity being associated with the firstthermal path, the method further comprising: conducting additional heatfrom a second component to the component mount; conducting theadditional heat from the component mount to the heat sink via a secondthermal path, a second thermal conductivity being associated with thesecond thermal path.
 6. A method of forming a substrate comprising:disposing one or more thermal planes in the substrate; providing a firstset of thermal vias in a component mounting area on a first side of thesubstrate, the first set of the thermal vias being thermally coupled tothe component mounting area and to the one or more thermal planes, wherea particular one of the one or more thermal planes is exposed at onesurface edge of the substrate and is not exposed at an opposing surfaceedge of the substrate; and providing a second set of thermal viasextending from a heat sink attachment area on the first side of thesubstrate, the second set of the thermal vias being thermally coupled tothe one or more thermal planes and to the heat sink attachment area,wherein the attachment area is on the first side of the substrateperpendicular to the exposed surface edge of the substrate.
 7. Themethod of claim 6, where the disposing one or more thermal planescomprises embedding one or more thermal planes in the substrate, the oneor more thermal planes having varying cross-sectional areas based on adistance of the embedded planes from the mounting area.
 8. The method ofclaim 6, where the providing the first set of thermal vias comprisesproviding through-holes extending from the component mounting area to aninterior of the substrate, the through-holes having varying diameters.9. The method of claim 6, further comprising: providing a thermalinterface material on at least a portion of the heat sink attachmentarea, the second set of the thermal vias being thermally coupled to thethermal interface material.
 10. The method of claim 6, where theproviding the first set of the thermal vias comprises providing aplurality of through-holes that extend from the component mounting areato a second component mounting area on an opposing side of thesubstrate, the plurality of through-holes being thermally coupled to thefirst and second component mounting areas.
 11. The method of claim 6,where the providing the first set of the thermal vias comprisesproviding a plurality of through-holes and plating at least a portion ofa circumference of the plurality of through-holes with a thermalconductor.
 12. The method of claim 11, where the plating comprisesplating a first of the plurality of through-holes with a first thermalconductor having a first thermal conductivity, and plating a second ofthe plurality of through-holes with a second thermal conductor having asecond thermal conductivity.
 13. The method of claim 11, where theplating comprises plating a first of the plurality of through-holes witha first volume of the thermal conductor, and plating a second of theplurality of through-holes with a second volume of thermal conductor.14. The method of claim 11, where the providing the plurality ofthrough-holes further comprises at least partially filling a volume ofthe plated through-hole with a second thermal conductor.